<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>weakSet案例</title>
    <style>
        *{
            padding: 0;
            margin: 0;
        }
        body{
            padding: 200px;
        }
        ul{
            list-style: none;
            display: flex;
            width: 200px;
            flex-direction: column;
        }
        li{
            height: 30px;
            border: solid 2px #e67e22;
            margin-bottom: 10px;
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding-left: 10px;
            color: #333333;
            transition: 1s;
        }
        a{
            border-radius: 3px;
            width: 20px;
            height: 20px;
            text-decoration: none;
            text-align: center;
            background: #16a085;
            color: white;
            cursor: pointer;
            display: flex;
            justify-content: center;
            align-items: center;
            margin-right: 5px;
        }
        .remove{
            border: solid 2px #eeeeee;
            opacity: 0.8;
            color: #eeeeee;
        }
        .remove a{
            background: #eeeeee;
        }
    </style>
</head>
<body>
    <ul>
        <li>houduren.com <a href="javascript:;">x</a></li>
        <li>hdcms.com <a href="javascript:;">x</a></li>
        <li>houdunwang.com <a href="javascript:;">x</a></li>
    </ul>
</body>
</html>


<script>
    class ToDos{
        constructor(){
            this.run();
        }
        run(){
            //得到所有的li对象
            this.items = document.querySelectorAll("ul>li");
            //定义一个weakSet
            this.lists = new WeakSet();
            //给weakSet中添加li元素
            this.record();
            this.addEvent();
        }
        addEvent(){
            this.items.forEach(item => {
                item.querySelector('a').addEventListener('click',event=>{
                    //检测wakeset中是否存在li元素
                    const parentElement = event.target.parentElement;
                    if(!this.lists.has(parentElement)){
                        parentElement.classList.remove('remove');
                        this.lists.add(parentElement);
                    }else{
                        //删除后从记录的wakeSet中移除
                        parentElement.classList.add('remove');
                        this.lists.delete(parentElement);
                    }
                });
            });
        }

        record(){
            this.items.forEach(item => this.lists.add(item));
        }
    }

    new ToDos();
</script>